In a redundant power supply system, electrical power is supplied by a plurality of power supplies electrically connected in parallel to one another. Generally, a desired system power requirement can be obtained by utilizing the combined output of N power supplies. By adding one additional backup power supply, resulting in N+1 power supplies in the power supply system, the system can electrically remove a failed power supply to avoid a power disruption and still meet the desired system power requirement of N power supplies.
Monitoring circuits have been developed that monitor the operation of a power supply by measuring a DC voltage at an output terminal on the power supply. However, a drawback with the other monitoring circuits is that the power supply may be malfunctioning for a relatively large amount of time before the fault condition causes a voltage or current variance at a power supply output terminal that is detected by the monitoring circuit.
Thus, there is a need for a monitoring system that can detect operational fault conditions in a power supply utilizing internal signals generated by the power supply, instead of merely monitoring a voltage at a power supply output terminal. Internal signals of a power supply are defined as any signal, such as a pulse width modulation signal for example, generated within a power supply to subsequently generate an output voltage at an output terminal of the power supply.